The situation, marred by militant violence and a last-minute delay, compromises hopes for a fair election.

Nigerian President Muhammadu Buhari urged Nigerians Friday "to go out and vote," promising adequate security for Saturday's postponed election which has put him in a tight race with businessman Atiku Abubakar.

In a televised morning address on the eve of the vote, Buhari asked Nigerians to put aside any doubts and place faith that the Independent National Electoral Commission (INEC) will rise to the occasion. "Do not be afraid of rumors of violence and unrest. Our security agencies have worked diligently to ensure that adequate security measures are in place," he said.

Buhari's rival Atiku, a former vice president who is representing the main opposition People's Democratic Party (PDP), made a similar appeal to voters through his Twitter feed Thursday night.

"This Saturday, a vote for PDP is a vote to get Nigeria working again. Come out, vote and #DefendYourVote," Atiku tweeted.

Buhari, a former military ruler who was later elected president in 2015, was criticized Monday for saying that anyone trying to intimidate voters or interfere with the voting "will do it at the expense of his own life."

Threats of violence have come from the Boko Haram militant group and its offshoot, Islamic State group in West Africa Province, who have carried out deadly sporadic raids in the northeast's Borno state. Boko Haram has warned people not to vote.

Campaign posters for Atiku Abubakar, leader of the People's Democratic Party (PDP) and President Muhammadu Buhari on the streets of Kano, Nigeria. | Source: Reuters

Last week, an attack by gunmen in the northwestern region killed more than 130, the Kaduna state governor Nasir el-Rufai said Tuesday. He added that it appeared to have been a deliberate plan to "wipe out certain communities,” but did not elaborate further.

Those killed in the attack were mainly from the Fulani ethnic group, who are usually Muslim and have been involved in clashes in recent years with people from the Adara ethnic group, who are predominantly Christian. El-Rufai said police were still investigating the motive for the attack and that there had been arrests.

Just five hours before the polls were supposed to open last weekend, the INEC announced a week's delay to voting in the early hours of last Saturday, just as some of Nigeria's 72.8 million eligible voters were preparing to go to polling stations. This has created a dilemma since many had spent considerable sums of money on travel last week.

Politicians and civil society groups said the delay could depress turnout which, in turn, would reduce the mandate of the eventual winner to rule Africa's most populous country and its biggest economy.

Last Saturday, Nigerian teacher Benjamin Shagu flew 310 miles from the city of Yola in the east of the country to the capital, Abuja, to vote in the presidential election -- only for the vote to be delayed. He said the sudden and last minute postponement means he likely won’t be able to vote in the end. Voters have to travel from their places of residence to vote in their constituencies where they are registered to vote.

"I have left my students for a week. I can't leave them for another week," said the English teacher - who traveled from the eastern city of Yola - weighing up the expense and disruption in returning to the city in which he registered to vote.

Members of Buhari's All Progressives Congress party and those of Atiku's PDP have accused one another of being behind the delay and colluding with the electoral commission.

Neither party has publicly provided evidence to back up their allegations.

The INEC's chairman Mahmood Yakoob has insisted that the vote will go ahead Saturday, blaming logistical reasons for the postponement, and said there had been no external pressure.

The two main candidates - President Muhammadu Buhari and former Vice President Atiku Abubakar - are both over 70 years old and have failed to generate significant excitement from a relatively youthful population.

"It disadvantages us because we need the turnout. Our base is the youth population, and they're the ones who can just easily get turned off from the whole process," Bukola Saraki, director general of Atiku's campaign, told Reuters in an interview. "The momentum was on our side," he said.

Nigerian fuel suppliers, incentivizing more participation from voters in the polls, have cut the price of petrol to encourage people to travel to cast their ballots, the information minister said Wednesday.

Information Minister Lai Mohammed said the Independent Petroleum Marketers Association of Nigeria (IPMAN) had cut the price of petrol at the pumps to US$0.39 per liter from US$0.40 from Friday to Monday.